J. Chem. Eng. Data 2009, 54, 1997–2001
1997
Adsorption Equilibria of L-(+)-Tartaric Acid onto Alumina Hasan Uslu*,† and I˙smail I˙nci‡ Department of Chemical Engineering, Engineering & Architecture Faculty, Beykent University, Ayazag˘a Ko¨yu¨, I˙stanbul, Turkey, and Department of Chemical Engineering, Engineering Faculty, I˙stanbul University, 34850, I˙stanbul, Turkey
The adsorption equilibria of L-(+)-tartaric acid onto alumina from wastewaters of wineries were studied, and it has been found that the equilibrium adsorption fits the Langmuir and Freundlich isotherms. Adsorption experiments were carried out at three different temperatures (298, 310, and 325) K. The adsorption of L-(+)tartaric acid is dependent on the acid concentration and the amount of alumina. The maximum percentage removal of L-(+)-tartaric acid was 22 % by alumina at 298 K. The Langmuir and Freundlich constants have been found to be 0.023 g · g-1 and 0.014 (g · g-1)/(L · g-1)-1/n, respectively, at 298 K. The thermodynamic 0 0 parameters ∆H ads and ∆S ads for the adsorption of tartaric acid on alumina have been calculated to be -5.62 -1 kJ · mol and 50.65 J · mol-1 · K-1, respectively.
Introduction Wastewaters from wineries contain tartaric acid. This acid is used in food processing and the pharmaceutical industry. The wastewaters from the winemaking process are the only industrial source for tartaric acid production.1 Many methods have been investigated to separate organic acids from aqueous solution. Solvent extraction has been used for purification of carboxylic acids,2,3 but the toxicity of the solvents used is always a problem. Electrodialysis has been used as a technique for the isolation and purification of carboxylic acids from fermentation media. Because other anions also go with the acid and other broth components end up in the product stream by diffusion, further processing is necessary to remove these impurities. The sorption of carboxylic acids on ion exchange resins has also been studied. This latter method requires additional chemicals to recover the acid from the resin. An alternative method of recovery of carboxylic acids from fermentation broth is based on adsorption.2 The adsorption of carboxylic acids by a number of substrates has been examined. For example, Aljundi examined the silicalite molecular sieve for adsorption of lactic acid.3 Inci investigated the adsorption of two carboxylic acids with activated carbon.4,5 In this study, the adsorption of L-(+)-tartaric acid on alumina is investigated. Adsorption processes are operative in most natural physical, biological, and chemical systems, and adsorption operations that employ solids such as alumina and synthetic resins are widely used in industrial applications and for purification and separation.6,7 The adsorption of carboxylic acids on alumina is very strong with adsorption energies much larger than those of other organic compounds. This is because most carboxylic acids are weak acids, and their degrees of dissociation in aqueous solutions are affected by the acidity of the medium. For example, the adsorption of aromatic acids on alumina is a strong function of the solution acidity. Although the adsorption of medium- and long-chain aliphatic carboxylic acids on alumina has been of * Corresponding author. E-mail:
[email protected]. † Beykent University. ‡ ˙ Istanbul University.
considerable interest because their property of forming selfassembled monolayers, the adsorption of water-soluble carboxylic acids on alumina has not been extensively studied.6 The nature of the interaction between the carboxylic group and hydroxyls on the surface has been studied by many investigators. In particular, the adsorption of aromatic acids on alumina has been studied. It is generally recognized that both oxygen atoms in the carboxylic group are anchored on the alumina surface, but two models have been proposed for the interaction. The bridging model considers that both oxygen atoms of the carboxylic group involved in the interaction are linked to Al-O sites on the surface through hydrogen bonding. The chelating model considers that the carboxylic group is dissociated and forms a bidentate linkage with a single Al-O-H site. The adsorption of carboxylic acids from aqueous solution onto the alumina surface is a dissociative adsorption process.8 The adsorbed carboxylic acids may interact with the alumina surface in such a way that a hydrogen atom is shared between each oxygen atom in the carboxylic group with an oxygen atom on the alumina surface forming a strong hydrogen bond.5 L-(+)-Tartaric acid is the dextro form of 2,3-dihydroxysuccinic acid. It has been known since antiquity in the form of its potassium salt, which occurs in grapes. In the fermentation of grape juice, the salt deposits in the fermentation vessels. The free crystallized L-(+)-tartaric acid was first obtained from such fermentation residues by Scheele in 1769. Tartaric acid is employed in the preparation of carbonated drinks, especially those that are grape flavored. It is widely used in effervescent tablets and powders and is frequently mixed with citric acid.9,10 There are many studies about the separation of tartaric acid from aqueous solution. In particular, activated carbon,11 copper,12 nickel,13 and oxidized nickel14 have been used to separate tartaric acid from wastewater streams. As¸ci15 removed some carboxylic acids from aqueous solution by using hydrogels. Ramsier et al.16 reported adsorption of phosphorus acids on alumina. Chakraborty et al.17 provided a theoretical insight into physical adsorption for a single-component adsorbent + adsorbate system. In this work, systematic studies of the adsorption of L-(+)tartaric acid from aqueous solutions have been investigated using alumina. Experimental results for the adsorption of L-(+)-tartaric
10.1021/je800976d CCC: $40.75 2009 American Chemical Society Published on Web 05/01/2009
1998
Journal of Chemical & Engineering Data, Vol. 54, No. 7, 2009
Table 1. Experimental Results of the Adsorption of L-(+)-Tartaric Acid onto Alumina 298 K
310 K
325 K
initial acid concn (g · L-1)
amount of alumina (g)
C (g · L-1)
Q (g · L-1)
C (g · L-1)
Q (g · L-1)
C (g · L-1)
Q (g · L-1)
58.79
0.05 0.10 0.15 0.20 0.25 0.05 0.10 0.15 0.20 0.25 0.05 0.10 0.15 0.20 0.25 0.05 0.10 0.15 0.20 0.25 0.05 0.10 0.15 0.20 0.25
57.37 55.75 51.41 48.38 45.66 100.81 97.78 96.06 94.44 87.47 160.17 155.76 150.61 147.27 143.23 203.54 198.79 186.57 180.61 168.38 318.69 298.59 283.43 273.53 264.34
1.42 3.04 7.38 10.41 13.13 2.72 5.75 7.47 9.09 16.06 3.83 8.24 13.39 16.73 20.77 6.56 11.31 23.53 29.49 41.72 9.90 30.00 45.16 55.06 64.25
57.62 55.72 52.53 49.77 47.21 101.11 98.98 97.68 95.64 88.96 160.51 156.14 151.93 148.52 144.84 205.20 199.84 188.18 182.36 169.94 320.13 300.45 285.28 275.68 266.57
1.17 3.07 6.26 9.02 11.58 2.42 4.55 5.85 7.89 14.57 3.49 7.86 12.07 15.48 19.16 4.9 10.26 21.92 27.74 40.16 8.46 28.14 43.31 52.91 62.02
58.01 56.27 53.62 50.96 48.42 101.76 99.84 98.52 97.04 90.16 161.05 157.03 152.90 149.77 145.76 206.31 201.07 189.73 184.55 171.24 322.21 302.62 287.34 278.19 268.87
0.78 2.52 5.17 7.83 10.37 1.77 3.69 5.01 6.49 13.37 2.95 6.97 11.1 14.23 18.24 3.79 9.03 20.37 25.55 38.86 6.38 25.97 41.25 50.4 59.72
103.53
164.00
210.10
328.59
acid by alumina at (298, 310, and 325) K are presented. All experimental data were then fitted using the Freundlich and Langmuir isotherm equations to obtain the parameters of each isotherm.18
Experimental Section L-(+)-Tartaric acid (purity > 99.5 %) and neutral (purity > 99.0 %) alumina were obtained from Merck. They were used without further treatment. We prepared L-(+)-tartaric acid stock solution by dissolving the appropriate amount of L-(+)-tartaric acid with distilled water in a flask. We prepared five different concentrations of L-(+)-tartaric acid solutions by diluting appropriate amounts of the stock acid solution. These concentrations were 5.82 %, 10.25 %, 16.25 %, 20.80 %, and 32.53 % (w/w). For the equilibrium studies, experiments were performed using 100 mL Erlenmeyer flasks at constant temperatures (298, 310, and 325) K in an electrical shaker. The prepared solutions (25 mL each) were placed in 100 mL Erlenmeyer flasks, which were previously cleaned and dried. To show the effect of the initial L-(+)-tartaric acid concentrations on the adsorption, 0.05 g, 0.10 g, 0.15 g, 0.20 g, and 0.25 g of alumina was agitated with 25 mL of the L-(+)-tartaric acid solutions at five different concentrations, 5.82 %, 10.25 %, 16.25 %, 20.80 %, and 32.53 % (w/w). All solutions were left in a temperature-controlled shaking bath at (298, 310, and 325) K for 2 h and were then kept for 24 h to reach equilibrium. Preliminary experiments were used to validate the time for the experiments to reach equilibrium. After the adsorption experiments, a known quantity of the adsorbate solutions was withdrawn from each bottle for analysis. Concentrations of the L-(+)-tartaric acid after filtration were determined by titration with 0.1 N aqueous sodium hydroxide. In most cases, the deviation between the amount of acid analyzed and the first prepared acid solutions did not exceed ( 1 %.
Results and Discussion Equilibria and Isotherms. Results for the adsorption of L-(+)tartaric acid on alumina are given in Table 1 and are illustrated in Figure 1. Figure 1 demonstrates the plot of C versus Q on
the adsorption of L-(+)-tartaric acid at 298 K. (Only data of 298 K were demonstrated in the Figures so as to prevent confusion.) Other results at different temperatures (310 and 325) K show the same trends as the result of 298 K. The adsorption of gas molecules or solutes in a solution onto the surface of a solid is an important phenomenon in physical chemistry, surface science, and industry. The plotting of isotherms is important to obtain an equation that represents the results and that could be used for the design of adsorption equipment. Adsorption isotherms depend on the specific surface area and the surface chemistry of solid adsorbents, the nature of adsorbates, and the acidity of the medium. The Langmuir isotherm is valid for monolayer adsorption onto a surface containing a finite number of identical sites. The model assumes uniform energies of adsorption onto the surface and no transmigration of adsorbate in the plane of the surface. When a physisorption process is carried out at a constant temperature, the amount adsorbed, Q, can be quantitatively described by the Langmuir equation. The Langmuir isotherm is represented by the following equation
C C 1 + ) Q KL·Q0 Q0
(1)
where C is the equilibrium concentration (milligrams per liter), Q is the mass adsorbed at equilibrium (milligrams per gram), KL is the Langmuir equilibrium parameter, and Q0 is the sorption maxima. A plot of C/Q versus C gives a straight line showing the applicability of the isotherm. Values of Q0 and KL at different concentrations have been determined from the slope and intercept of the plot. The Langmuir adsorption parameters are very useful in predicting adsorption capacities and for incorporating a mass transfer relationship. This shows a system that exists with a monolayer coverage of the adsorbent on the surface of the adsorbate. The isotherms are shown in Figure 2. The values of the isotherm parameters are given in Table 2. The Freundlich equation is used for heterogeneous surface energies in which the energy term in the Langmuir equation varies as a function of the surface coverage strictly because of
Journal of Chemical & Engineering Data, Vol. 54, No. 7, 2009 1999
Figure 1. Plot of Q versus C for adsorption L-(+)-tartaric acid at 298 K: 2, 58.79 (g · L-1); *, 103.53 (g · L-1); ×, 164.00 (g · L-1); b, 210.10 (g · L-1); 9, 328.59 (g · L-1).
Figure 2. Langmuir isotherm for amount of 0.05 g L-(+)-tartaric acid at different temperatures: [, 298 K; 9, 310 K; 2, 325 K. Table 2. Freundlich and Langmuir Isotherm Parameters of L-(+)-Tartaric Acid onto Alumina Freundlich parameters temperature (K)
Log Kf
298 310 325
-1.85 -1.90 -2.21
-1
Langmuir parameters
-1 -1/n
Kf (g · g )/(L · g ) 0.014 0.012 0.006
the variation in the heat of adsorption. The Freundlich equation has the general form
Q ) Kf·C1/n
(2)
A logarithmic plot linearizes the equation enabling the exponent n and the constant Kf to be determined.18-21
log Q ) log Kf + (1/n) log C
(3)
The constants are listed in Table 2 for the batch system. The values of Kf and 1/n at different concentrations were determined from the slope and intercept of the linear plots of log Q versus log C.21-24 Data are shown in Figure 3. (Only data with the optimum amount of alumina, 0.5 g, are demonstrated in the Figures so as to prevent confusion.) The values of the isotherm parameters are given in Table 2. The obtained fits show that
n
R
1/Q0
KL (g · g-1)
R2
0.88 0.88 0.83
0.96 0.99 0.99
4.01 2.79 2.91
0.023 0.022 0.021
0.99 0.98 0.94
2
adsorption of tartaric acid from wastewater onto alumina obeys both isotherms. Effect of Temperature. The effect of temperature on the adsorption of tartaric acid onto the alumina was studied at (298, 310 and 325) K. Table 1 shows results of adsorption efficiency at the different temperatures. It can be seen from Table 1 that the adsorption capacity of the alumina decreases with increasing temperature. As related to the temperature effect, the thermodynamic parameters have been calculated for this adsorption system. The 0 , first parameter is Gibbs energy change of adsorption, ∆G ads which was calculated by using equation
∆G 0ads ) -R·T·ln KL
(4)
where R is the universal gas constant and T is the temperature in kelvins. KL is the thermodynamic equilibrium constant for
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Figure 3. Freundlich isotherm for 0.05 g L-(+)-tartaric acid at different temperature: [, 298 K; 9, 310 K; 2, 325 K.
Figure 4. van’t Hoff plot of ln KL against 1/T. Table 3. Thermodynamic Parameters for Adsorption of Tartaric Acid onto Alumina at Different Temperatures temperature K 298 310 325
0 ∆G ads -1
kJ · mol
-7.76 -7.96 -8.22
0 ∆S ads -1
0 ∆H ads -1
J · mol · K 50.65
kJ · mol-1 -5.62
the adsorption process that was determined by plotting ln(C/Q) versus C and extrapolating to zero C, as suggested by Khan and Singh.25 The other thermodynamic parameters, the enthalpy change, 0 0 , and the entropy change, ∆S ads , were calculated from the ∆H ads slope and intercept of the plot of ln K0 against 1/T according to the van’t Hoff equation
ln KL )
∆S 0ads ∆H 0ads R R·T
(5)
∆H 0ads was obtained from the slope of the straight line, and ∆S 0ads was determined from the intercept of the graph26,27 (Figure 4). To evaluate the thermodynamic equilibrium constant, KL, we plotted the C/Q values versus the C values at (298, 310, and 325) K, as seen in Figure 2. Linear graphs were obtained for all temperatures. The KL parameters obtained were used to 0 function.28 The calculated thermodynamic calculate the ∆G ads
parameters (∆H 0ads, ∆S 0ads, and ∆G 0ads) at the temperatures above are given in Table 3.
Conclusions In this study, the adsorption of L-(+)-tartaric acid onto alumina has been investigated, and it has been found that the adsorption fits the Langmuir and Freundlich isotherms at different temperatures. The maximum percentage removal of L-(+)-tartaric acid was 22 % by alumina at 298 K. Thermody0 , namic parameters of tartaric acid adsorption such as ∆H ads 0 0 ∆S ads, and ∆G ads have been calculated.
Literature Cited (1) Mourgues, J.; Maugenet, J. Re´cupe´ration des sels de l’acide tartrique dans les eaux re´siduaires des distilleries vinicoles. Ind. Aliment. Agric. 1975, 92, 11–16. (2) Aljundi, I. H.; Belovich, J. M.; Talu, O. Adsorption of lactic acid from fermentation broth and aqueous solutions on zeolite molecular sieves. Chem. Eng. Sci. 2005, 60, 5004–5009. (3) Aljundi, I. H. Fermentation and Separation of Lactic Acid. Ph.D. Dissertation, Cleveland State University: Cleveland, OH, 2005. (4) Inci, I. Investigation of adsorption of gluconic acid from aqueous solutions by activated carbon. Asian J. Chem. 2002, 15, 325–330. (5) Inci, I. Adsorption of glycolic acid by activated carbon. ReV. Chim. 2003, 54, 199–201. (6) Mao, Y.; Fung, B. M. A Study of the adsorption of acrylic acid and maleic acid from aqueous solutions onto alumina. J. Colloid Interface Sci. 1997, 191, 216–221.
Journal of Chemical & Engineering Data, Vol. 54, No. 7, 2009 2001 (7) Deshmukh, M. R.; Shah, S. M.; Katade, S. R.; Belhekar, A. A.; Kashalkar, R. V.; Deshpande, N. R. Removal of methylene blue and malachite green by agricultural waste material stalks of Cajanus cajan. Asian J. Chem. 2004, 16, 1863–1867. (8) Mao, Y.; Fung, B. M. A study of the adsorption of acrylic acid and maleic acid from aqueous solutions onto alumina. J. Colloid Interface Sci. 1997, 191, 216–221. (9) Kirk-Othmer Encyclopedia of Chemical Technology; Wiley: New York, 1981. (10) Gusler, G. M.; Browne, T. E.; Cohen, C. Sorption of organic acids from aqueous solution onto polymeric resins. Ind. Eng. Chem. Res. 1993, 32, 2727–2735. (11) Fahimuddin, G. K.; Zafaruddin, K. Thermodynamics of adsorption of tartaric acid from aqueous solution on the surface of activated charcoal. J. Pure. Appl. Sci. 2001, 20, 97–105. (12) Yan, H. J.; Wang, D.; Han, M. J. Adsorption and coordination of tartaric acid enantiomers on Cu(111) in aqueous solution. Langmuir 2004, 20, 7360–7364. (13) Humblot, V; Haq, S; Muryn, C. From local adsorption stresses to chiral surfaces: (R,R)-tartaric acid on Ni(110). J. Am. Chem. Soc. 2002, 124, 503–510. (14) Jones, T. E.; Baddeley, C. J. An investigation of the adsorption of (R,R)-tartaric acid on oxidised Ni{111) surfaces. J. Mol. Catal. A: Chem. 2004, 216, 223–231. (15) As¸ci, Y. S.; Hasdemir, I˙. M. Removal of some carboxylic acids from aqueous solutions by hydrogels. J. Chem. Eng. Data. 2008, 53, 2351– 2355. (16) Ramsier, R. D.; Henriksen, P. N.; Gent, A. N. Adsorption of phosphorus acids on alumina. Surf. Sci. 1998, 203, 72–88. (17) Chakraborty, A.; Saha, B. B.; Choon, K.; Koyama, S.; Srinivasan, K. Theoretical insight of physical adsorption for a single-component adsorbent + adsorbate system. I. Thermodynamic property surfaces. Langmuir 2009, 25, 2204–2211.
(18) Pierce, M. L.; Moore, C. B. Adsorption of arsenite and arsenate on amorphous iron oxide. Water Res. 1982, 16, 1247–1253. (19) Saleh, M. I.; Adam, F. Adsorption isotherms of fatty acids on rice hull ash in a model system. Ibid 1994, 71, 1363. (20) Rai, K.; Maheshwari, A. Removal of pollutants from industrial effluents using plastic clay and pyrophyllite. Asian J. Chem. 2002, 14, 739– 745. (21) Nouri, S. Effect of different treatment on the adsorption of p-cresol by activated carbon. Asian J. Chem. 2002, 14, 934–942. (22) Morenocastilla, C.; Riverautrilla, J. Adsorption of some substituents on activated carbon from bituminous coal. Carbon 1995, 33, 845– 851. (23) Shastri, S. S.; Yankie, M. K. N. Evaluation of different grades of granular activated carbon adsorbents for scavenging priority pollutants from wastewater. Asian J. Chem. 2002, 14, 1009–1026. (24) Gupta, S.; Bhatnagar, M. Removal of zinc and cadmium by activated carbon adsorption. Asian J. Chem. 2002, 14, 1031–1034. (25) Khan, A. A.; Singh, R. P. Adsorption thermodynamics of carbofuran on Sn(IV) arsenosilicate in H+ Na and Ca 2+ forms. Colloid Surf. 1987, 24, 33. (26) Tahir, S.; Rauf, N. Thermodynamic studies of Ni(II) adsorption onto bentonite from aqueous solution. J. Chem. Thermodyn. 2003, 35, 2003– 2009. (27) Gupta, V. K.; Singh, P.; Rahman, N. Adsorption behavior of Hg(II), Pb(II), and Cd(II) from aqueous solution on Duolite C-433: a synthetic resin. J. Colloid Interface Sci. 2004, 275, 398–402. ¨ . Adsorption thermodynamics of (28) Demirbas, A.; Sari, A.; Isildak, O stearic acid onto bentonite. J. Hazard. Mater. 2006, 135, 226–231.
Received for review October 29, 2008. Accepted April 4, 2009.
JE800976D
